1. Field of the Invention
The present invention relates to a novel sterol derivative having an effect of remedying chapped skin and a surface-activating effect, as well as, being useful as a base for cosmetics, toiletries or medicines.
The present invention also relates to a process for producing said novel sterol derivatives.
Further, the present invention relates to a dermatologic external preparation, more particularly, to a dermatologic external preparation whereby the water retention capability of the corneal layer is elevated and thus the chapped skin can be remedied.
2. Description of the Related Art
It has been known that moisture contained in the corneal layer is important for moistening and softening the skin. It is thought that water soluble components contained in the corneal layer, namely, free amino acids, organic acids, urea or inorganic ions contribute to the retention of moisture. Either one of these substances or a combination thereof has been used in medicinal dermatologic external preparations or cosmetics in order to remedy or prevent chapped skin. Separately, a number of humectants having strong affinities for water have been developed and employed for similar purposes as those described above.
It has been recently found that a lipid present in an inter-corneal-cellular space forms a lamellar structure in the presence of water to play an important role in retaining moisture of the corneal layer [see G. Imokawa, M. Hattori, J. Invest. Dermatol., 84, 282 (1985)].
Further it has been elucidated that among the intercellular lipids, ceramides and cholesterol esters, in particular, have an improved effect of remedying chapped skin when they are applied on the skin [see G. Imokawa et al., Arch. Dermatol. Res., 281, 45 (1989)].
In addition, it has been attempted to moisten and to soften the skin with an artificial intercellular lipid comprising a substance analogous to the inter-corneal-cellular lipid to obtain a relatively excellent improving effect [see Genji Imokawa, Fragrance Journal, 4, 26 (1990), and Genji Imokawa, et al., "Kinosei Keshohin (Functional Cosmetics)", 235, published by CMC (1990)].
However, the application of humectants such as water soluble components contained in the corneal layer to the skin is effective merely in supplying moisture to the corneal layer on the skin corneal layer, and the effect is only temporary. It is, therefore, impossible to fundamentally improve the water retention capability of the corneal layer to thereby essentially prevent or treat chapped skin thereby.
On the other hand, although the water retention function of tile corneal layer can be improved and the skin can be prevented from chapping or chapped skin can be remedied to some extent by applying the artificial intercellular lipid to the skin, no healthy skin can be completely recovered to the previous level, so that the effect of the artificial intercellular lipld is not yet satisfactory.
Under these conditions, it has been eargerly demanded to develop a base for an external preparation for the skin and a dermatologic external preparation which are capable of fundamentally improving the water retention capacity of the corneal layer of chapped skin to restore the function of the skin to a level equal or superior to that of the healthy living body and also moistening and softening the skin.